Low genetic variation detected within the widespread mangrove species Nypa fruticans (Palmae) from Southeast Asia

Genetic diversity within and among six natural populations of Nypa fruticans from China, Vietnam, and Thailand was assessed using SSR and ISSR analysis. Our results showed an extremely low level of genetic diversity of N. fruticans (at the species level, P = 11.76% and 2.88%, He = 0.0279 and 0.0113, I = 0.0470 and 0.0167 by SSRs and ISSRs, respectively) across a total of 183 individuals. No genetic variation was detected within any population except for the Thailand population by SSRs (P = 11.76%, He = 0.0417; I = 0.0622). The bottlenecks during glacial epochs, founder effects, and propagation pattern may be responsible for the extremely low level of genetic diversity of N. fruticans.     

Allozyme variation of the endangered endemic plant Myricaria laxiflora: Implications for conservation

Myricaria laxiflora, a riparian plant that naturally occurs in the riverbanks of the Yangtze River Valley, has become extinct across its entire geographical distribution range in the wild due to the construction of the Three Gorges Dam. The allozyme variation of M. laxiflora populations was investigated in the present study. Mean number of alleles per locus (A) was 2.35, and the observed heterozygosity (H_o) and expected heterozygosity (H_e) were 0.35 and 0.30, respectively. Six populations showed significant excesses of heterozygotes based on the examination of a multilocus fixation index (F_IS). The population genetic divergence of M. laxiflora is high (G_ST = 0.144 and ?_B = 0.131) and the analysis of molecular variance analysis shows that 19.71% of the total genetic variation is caused by the difference between populations. Based on the obtained genetic information, six management units have been identified, all of which are expected to enhance the effective management of the remaining and transplanted individuals of this endangered species in the future.     

Analysis of diversity and relationships among Chinese orchid cultivars using EST-SSR markers

Chinese orchid (Cymbidium spp.) is an important potted flower with extremely high ornamental value in China. It is important to identify the genetic diversity of its germ plasma resources for development and evaluation of its cultivars. A set of 13 expressed sequence tag (EST)-derived simple sequence repeat (SSR) was used to analyze 103 cultivars of six species of Chinese orchid, namely Cymbidium goeringii, C. faberi, Cymbidium ensifolium, C. kanran, C. sinense and C. goeringii var. longibracteatum. The 13 SSR primer pairs generated a total of 168 polymorphic bands, with an average of 12.92 bands per primer and a range of 6–24 bands which clearly revealed the difference between cultivars inter- or intra-species of Chinese orchid. Cluster analysis based on UPGMA, NJ and PCoA method showed a dendrogram with three basic clusters and splitting feature of C. ensifolium and C. goeringii which partially congruent with the current taxonomic classification.     

Development,characterization and utilization of genomic microsatellite markers in turmeric (Curcuma longa L.)

Development of a robust set of 18 genomic microsatellite markers from turmeric (Curcuma longa L.) and its effective utilization in estimating the genetic diversity of 20 turmeric accessions are described. A total of 103 alleles were detected with an average of 5.7 alleles per locus. These markers displayed varied levels of polymorphism as evident from its discriminating power ranging from 0.19 to 0.70. The UPGMA cluster analysis of genetic distance values resolved the 20 turmeric accessions into five main groups. Three sets of genetically identical accessions were detected within the analyzed accessions, suggesting a revisit of the germplasm collection strategy based on vernacular identity. The entire grouping pattern of the entities was loose and independent of their geographical origins. These polymorphic SSR markers would be useful for the population genetic studies and germplasm management of turmeric.     

No loss of genetic diversity in small and isolated populations of Medicago sativa subsp. falcata

Molecular allozyme markers of three polymorphic isozymes were used to estimate the genetic diversity among the seed progeny in fragmented Estonian populations of sickle medic Medicago sativa ssp. falcata L. depending on the population size and the isolation degree. Genetic diversity H_e was high in all populations, ranging between 0.795 and 0.893. No correlation between the genetic diversity measures and population size or isolation distance was found. Even the smallest population had equally high genetic diversity as about a hundred times larger population. Genetic differentiation of populations into two major groups was associated with the geographic position of populations, except one remote population. Elimination of seed progeny of reduced fitness by embryo abortion and continuous yearlong contribution of the highly heterozygous progeny through the soil seed bank are considered as important supplementary factors that have contributed to maintaining high levels of genetic diversity in populations of sickle medic in addition to its autotetraploid nature and perennial life form.     

A comparative analysis of genetic diversity in medicinal Chrysanthemum morifolium based on morphology, ISSR and SRAP markers

The diversity and genetic relationship among 29 populations of Chrysanthemum morifolium, one of Chrysanthemum indicum and one of Chrysanthemum nankingense from China were analyzed using morphological traits and molecular markers. Twenty morphological traits were scored as well as 182 ISSR marker-fragments, as amplified by 22 primers [the percentage of polymorphic bands (PPB): 81.87%], and 243 SRAP marker-fragments as generated by 26 primer pairs (PPB: 75.72%). Mantel’s test indicated significant correlation (r = 0.624) of morphological trait and SRAP. By contrast, the morphological trait showed low correlation with ISSR (r = 0.246). Cluster analysis showed groupings of the accessions according to all four methods correlated well with their geographic region of origin, and most populations from the south of China were classified into one cluster and most populations from the north of China were classified into another cluster. Finally, an appropriate strategy for conserving the C. morifolium germplasm was proposed.     

Assessment of the genetic diversity among Glyptosternum maculatum, an endemic fish of Yarlung Zangbo River, Tibet, China using SSR markers

The genetic diversity of Glyptosternum maculatum populations from Nyang River, Lhasa River, and Shetongmon Reach of Yarlung Zangbo River was assessed using six microsatellite markers. Overall, the genetic diversity across the three populations was low. The Shetongmon population exhibited the highest level of genetic diversity in terms of number of alleles and effective alleles, heterozygosity, and polymorphic information content value, followed by the Nyang population and Lhasa population. The analysis of molecular variance demonstrated that almost the variation (86.64%) occurred within populations. The differentiation among populations was not significant, and population structure was weak. These results revealed that three natural populations of G. maculatum are not genetically differentiated and the large disparity of living altitude did not caused genetic differentiation between different populations. Our observations will help identify the genetic relationship among populations to understand the genetic diversity of G. maculatum.     

Woody Encroachment Removal from Midwestern Oak Savannas Alters Understory Diversity across Space and Time

Recovering biodiversity is a common goal during restoration; however, for many ecosystems, it is not well understood how restoration influences species diversity across space and time. I examined understory species diversity and composition after woody encroachment removal in a large-scale savanna restoration experiment in central Iowa, United States. Over a 4-year time series, restoration had profound effects across space and time, increasing richness at local and site-level scales. Restoration sites had increased α (within sample) Simpson's diversity and α and γ (site level) species richness relative to control sites, although γ and β (among sample) Simpson's diversity, β richness, and α species evenness were not affected. Changes in richness were driven by graminoids at the α and γ scales and woody species (and some evidence for forbs) at the α scale. Interestingly, indicator species analysis revealed that at least some species from all functional groups were promoted by restoration, although no species were significant indicators of pre-treatment or control sites. Both savanna and nonsavanna species were indicators of restored sites. Restoration promoted exotic species at both scales, although species with spring phenologies were unaffected. Woody encroachment removal may be a means to promote species establishment in savannas; however, in this study, it resulted in establishment and proliferation of native and exotic and savanna and nonsavanna species. Future work might consider reintroduction of key savanna species to supplement those that have established. Work like this demonstrates the utility of restoration experiments for conducting research on large- and multiscale processes, such as species diversity.     

Evaluating Wetland Restoration Success Using Aquatic Macroinvertebrate Assemblages in the Sacramento Valley,California

Currently, there is little professional consensus as to which ecological metrics should be used to measure restoration success in wetlands. Aquatic macroinvertebrate communities have many qualities to recommend them as useful metrics in this manner; yet, they have not been widely used to evaluate wetland restoration success. We examined the macroinvertebrate communities of four restored seasonal wetlands across a chronosequence of postrestoration age and compared them to a remnant natural wetland in the Central Valley of California. We examined two qualitatively different sets of aquatic macroinvertebrate metrics, general measures of community properties (abundance, richness, and diversity) and specific assemblage membership (nonmetric multidimensional scaling and permutational multivariate analysis of variance). Our results using these two different sets of metrics give us different answers. The general measures suggest that wetland macroinvertebrate communities converge on relatively stable values sometime after 10 years postrestoration. The specific assemblage results imply that the particular set of taxa found in restored wetlands is not predictable over the chronosequence we examined. Taken together, our results suggest that aquatic macroinvertebrate communities may be useful for measuring some aspects of restoration success but that there is unlikely to be a final aquatic community pattern indicating restoration success.     

The coconut palm,Cocos nucifera,impacts forest composition and soil characteristics at Palmyra Atoll,Central Pacific

Question: Cocos nucifera, the coconut palm, has a pantropical distribution and reaches near monodominance in many atolls, low lying islands and coastal regions. This paper examines the ecological correlation between C. nucifera abundance and changes in forest structure, floristic diversity and forest soil characteristics. Location: Palmyra Atoll NWR (USA), Central Pacific Ocean. Methods: Plant surveys were conducted on 83 transects (each 100 m²). All plants ≥5 cm in height were identified and counted; large plants were also measured and ground cover was surveyed. Major macronutrients, pH, macro‐elements/base cations, micronutrients and pedogenic elements, and thermodynamic stability levels were quantified from soil samples taken at each transect. Results: Even in a low diversity atoll environment, we found that high abundances of C. nucifera corresponded with pronounced differences in forest communities including: lower diversity of established trees and regenerating understorey; higher stem density and stand basal area; lower abundance of major macronutrients; and differences in macro and trace elements and energy content of soil organic matter. Historical natural experiments document that the expansion of C. nucifera was the likely causative agent of these changes. Discussion: Cumulatively, these data show that C. nucifera has important impacts on floristic, structural and soil characteristics of forests where it becomes dominant. Given the high proportion of tropical coastal areas in which C. nucifera is now naturalized and abundant, this likely has important implications for coastal forest diversity and structure.